Re: Tree-sitter introduction documentation

[Gregory Heytings]

> > Good luck with that!  It requires to install Node.js and other stiff, 
> > which I personally won't touch with a 3-mile pole, and I'm unsure (but 
> > never bothered to find out) whether free replacements even exist.
>
> That's the part of Tree-sitter which makes me a bit uneasy.
>
> In Emacs, we usually don't just stick to the letter of the Free Software 
> principles (e.g. release our code under the GPL) but we try to go the 
> extra miles so that our users can actually exercise their rights as 
> easily as possible (e.g. with things like `C-h k` that lets them jump 
> straight to the source, ...).
>
> But with Tree-sitter, our users are currently a bit stuck.  The grammars 
> are Free, yes, but it takes a fair bit of extra work (and potentially 
> even some code with unclear licensing along the way) if you want to 
> modify their source code and use the result :-(

I think that's an exaggeration.  On a Debian-based system, building a 
grammar from source is as easy as typing three commands:

$ apt install gcc nodejs rust-all
$ cargo install tree-sitter-cli
$ tree-sitter generate grammar.js

Step 1 installs the necessary tools, all of which are free software (GPL 
for GCC, MIT for Node.js, dual MIT and Apache for Rust).

Step 2 downloads the source code of tree-sitter and of all its 
dependencies, and builds tree-sitter.  Again it is, and its dependencies 
are, free software (MIT for tree-sitter, and for its dependencies usually 
dual MIT and Apache like Rust itself, sometimes BSD or Zlib or public 
domain).

Step 3 converts the grammar.js file into the parser.c file.

Now you can use GCC to build the library.